Washer for tanks

ABSTRACT

A tank washer comprising a housing which supports reciprocating spray nozzles for spaying the walls of a tank which is to be cleaned with a cleaning liquid. The reciprocation of the spray nozzles is controlled by a piston that reciprocates in the housing under the force of the cleaning liquid. A piston assembly for use in a tank washer comprising a piston head and a connecting rod having one end connected to said piston head. The piston is mounted in a piston chamber for reciprocation.

FIELD OF THE INVENTION

This invention relates to a washer for tanks and more particularly to awasher for tanks of the type that may be used for containing liquids,food products, industrial liquids or the like and which require cleaningfrom time to time to remove deposits left by the materials or to readythe tank to receive a different material without fear of contaminationby the previous material held in the tank.

BACKGROUND OF THE INVENTION

The washer which is described in this patent application cleans theinterior of a tank by spraying continuous streams of a cleaning liquid,usually water, at high pressure against the interior sidewalls of thetank.

This is accomplished by a washer which is relatively inexpensive tomanufacture and which can operate for very long periods withoutrequiring maintenance.

SUMMARY OF THE INVENTION

With the foregoing in mind, the invention relates generally to a washerfor tanks comprising a housing that includes a liquid inlet is provided.A plurality of nozzles are supported on the housing for reciprocation inan arc about an axis. A piston which is in the housing reciprocates inresponse to some of the liquid entering the housing along another axis.Means are provided for connecting the piston to the nozzles so thatreciprocation of the piston causes the nozzles to reciprocate as therest of the liquid flows through the nozzles to wash the tank.

In a further aspect of the invention, a piston assembly for use in ahousing which is part of a washer for tanks is provided. The pistonassembly includes a piston chamber in which a piston is mounted forreciprocation and a connecting rod. The piston head has one endconnected to the piston head. The piston is mounted in a washer forreciprocation. The piston head includes a liquid inlet and two liquidoutlets. Means are provided in the piston head for directing liquidentering the piston head alternately through the liquid outlets to causethe piston to reciprocates in the piston chamber so that the connectingrod can drive a crankshaft through an arc.

DESCRIPTION OF THE DRAWING

FIG. 1 is a side elevation view of a washer for tanks constructed inaccordance with the presently preferred form of the invention.

FIG. 2 is a side elevation of the washer for tanks shown in FIG. 1, butwith part of its side broken away to show its interior.

FIG. 3 is a partially exploded side elevation view of the nozzle andcrankshaft assembly for the washer for tanks shown in FIG. 1.

FIG. 4 is a section view taken along line 4-4 of FIG. 3.

FIG. 5 is a section view taken along lines 5,5′-5,5′ of FIG. 3.

FIG. 6 is a side elevation view, partially in section of a portion ofthe washer for tanks shown in FIG. 1.

FIG. 7 is a side elevation view, partially in section, of the interiorof the piston chamber of the washer for tanks shown in FIG. 1.

FIGS. 8A and 8B are an exploded perspective view, partially in sectionof the piston head and connecting rod contained within the pistonchamber shown in FIG. 7.

FIG. 9 is a section view taken along line 9-9 of FIG. 8A.

FIG. 10A is a view partially in section of the configuration of thepiston head when it is moving up within the piston chamber.

FIG. 10B is a view partially in section of the configuration of thepiston head when it is moving down within the piston chamber.

FIG. 11A is a schematic view of the forces applied to a part of theinvention which enable the piston head to change its direction ofmovement.

FIG. 11B is a schematic view of the forces applied to the part of theinvention shown in FIG. 11A which enable the piston head to change itsdirection of movement from that shown in FIG. 11A.

DETAILED DESCRIPTION OF A PRESENTLY PREFERRED FORM OF THE INVENTION

Now referring to the drawing for a detained description of a presentlypreferred form of invention, there is seen in FIG. 1 a washer for a tank10 has a having a housing 14 with a liquid inlet 16, a piston chamber 20and a nozzle and crankshaft assembly 24 contained substantially insidethe housing 14. Externally, the hub 26 of the nozzle and crankshaftassembly 24 and nozzles 30 can be seen.

Referring to FIGS. 2 and 3, the nozzle and crankshaft assembly 24 is agenerally elongated hollow element with an axial opening 28. At one endthe nozzle and crankshaft assembly 24 includes the hub 26 of the nozzleassembly which provides a liquid connection between the interior of thehousing 14 and the nozzles 30. The nozzle and crankshaft assembly 24 issupported in the housing 14 for rotation about an axis 34.

Immediately adjacent the hub 26 of the nozzle assembly is a nozzle hubsupport 44 which comprises a hollow section of reduced outer diameter.The nozzle hub support 44 bears against the interior surface of O-ring46 which is supported in the housing 14 while the inner face 48 ofnozzle hub support 44 bears against the end wall of O-ring 46 so that aliquid tight relation is maintained between them.

Immediately adjacent the nozzle hub support 44 is a further hollowsection 54 of reduced outer diameter comprising a front portion 56 and arear portion 60 which are separated by a cut-out 64. The front portion56 is provided with a plurality of circumferentially space openings 66(only one of which is shown) to enable liquid which is in the housing 14to enter the axial opening 26 of the of the nozzle and crankshaftassembly 24.

As best seen in FIG. 4, the cut-out 64 is of sufficient depth so that itextends substantially entirely through the further hollow section ofreduced diameter 54 so that the remnant of the axial opening 26 definesan elongated groove 70.

Immediately adjacent the rear portion 60 of the further hollow sectionof reduced diameter 54 is a ratchet assembly 80 which will be describedin detail herein.

But for now, the ratchet assembly 80 includes a hollow cylindricalsection 84 whose axial opening is a part of axial opening 26. Thediameter of hollow cylindrical section 84 is slightly less than thediameter of further hollow section of reduced diameter 54 so that itsjuncture with further hollow section of reduced diameter 54 forms abearing surface 86 against which a bevel gear, which will be describedin detail, bears when the bevel gear is supported on the outer wall 88of hollow cylindrical section 84. The ratchet assembly 80 is operativeto cause the housing 14 to rotate relative to the liquid inlet 16 aswill be made apparent.

A hollow cylindrical member 96 with external threads 98 is connected tohollow cylindrical section 84. The opening in hollow cylindrical section96 is part of the axial opening 26 in the nozzle and crankshaft assembly24.

As seen in FIGS. 3, 4, and 5, a torsion rod 108 has one end fixed in theend wall 112 of reduced diameter section 54. Preferably, it resides inthe elongated groove 70 formed by the cut-out 64.

Referring to the ratchet assembly, 80, the hollow cylindrical section 84has a slot 116 in its peripheral wall.

As best seen in FIGS. 3 and 5, the interior wall of the hollowcylindrical section 84 includes a longitudinally extending notch 118. Apawl 124 which is an elongated generally arcuate member has one end 126in engagement with the notch 118 and its other end 128 extending throughthe slot 116 in hollow cylindrical section 84.

A bevel gear 130, which was mentioned earlier, is shown in FIG. 3exploded to the left of the of hollow cylindrical section 84 and pawl124 which support it. As seen in FIG. 5, the interior circumference ofthe bevel gear 130 is provided with a plurality of teeth 134 which canreceive the other end 128 of the pawl 124. Thus, as seen in FIGS. 4 and5, when the nozzle and crankshaft assembly 24 move clockwise in thedirection of arrow “A”, the bevel gear 130 remains fixed relative to thehousing 14 since the pawl 124 yields under the force of the torsion rod70 to enable it to slip from tooth to tooth 134 on the interior of thebevel gear 130.

However, when the nozzle and crankshaft assembly 24 movecounter-clockwise in the direction of arrow “B” as shown in FIGS. 4 and5, the pawl 124 engages the teeth 134 on the interior surface of thebevel gear 130 and causes the bevel gear 130 to rotate with it.

The bevel gear 130 is an important part of the mechanism for enablingthe washer 10 to pivot about an axis that is in alignment with theliquid inlet to the housing 14 in a series of discrete steps as will bemore fully explained.

As seen in FIG. 2, the rear wall of the bevel gear 130 (removes for thesake of clarity of the drawing) bears against a collar 150 on theinterior of the housing 14 to restrain it against rearward axialmovement on the reduced diameter section 54. Thus, as earlier explained,forward axial movement of the bevel gear 130 is restrained by bearingsurface 86.

The nozzle and crankshaft assembly 24 is held in the housing 14 by anend cap 146 (FIG. 2) which threadingly engages the aforementionedexternal threads 98 on hollow cylindrical member 96 and which bearsagainst an O-ring which is seated in the housing 14.

The liquid inlet 16 can best be seen in FIGS. 2 and 6. It comprises, inpart, a collar 150 with a smooth interior wall which defines a bearingsurface 152. The collar 150 has a reduced diameter lower section 158which has external threads to engage complimentary internal threads onan internal collar 166 in the upper portion of the housing 14. SuitableO-rings are provided to reduce the likelihood of liquid leakage betweenthe parts.

Contained within the smooth interior wall and in engagement with thebearing surface 152 in collar 150 is an elongated hollow sleeve 180which has an upper portion 182 which extends above the collar 150 andwhich has external threads 184. Its lower portion 190 includes a bevelgear 190 which is in driven relationship with earlier mentioned bevelgear 130 which is seen best in FIGS. 3 and 6.

A second collar 194 has at its lower end internal threads 196 which arecomplementary to and engage external threads 182. At its upper end,collar 194 has internal threads 200 which can be connected tocomplementary threads on a liquid supply pipe 204.

It should be noted that elongated hollow sleeve 180 and bevel gear 190along with collar 194 are fixed to the liquid supply pipe 204.Accordingly, they are incapable of movement. However, the collar 150 isfree to rotate about an axis defined by the liquid supply pipe 204.

As explained earlier, the housing 14 is connected to the collar 150.Accordingly, both the collar 150 and the housing 14 can rotate togetherabout the liquid supply pipe 204.

The manner in which this rotation is accomplished will now be described.

As best seen in FIGS. 2 and 7, the piston chamber 20 may be generallycylindrical. It includes a side wall 210 and a bottom wall 212. Its topwall 214 is defined by the bottom wall of a cylindrical member 216extending downwardly from the lower part of housing 14 and which hasexternal threads.

As seen in FIGS. 2 and 7, the piston chamber 20 includes internalthreads that engage the external threads on the cylindrical member 216to connect the piston chamber 20 to the housing 14. The top wall 214includes an upwardly extending collar 226 having a central opening 228surrounded by a bushing 230.

A first drain opening 234 is provided in the upper portion of thesidewall 210. A second drain opening 236 is provided in the bottom wall212.

As best seen in FIGS. 7, 8A and 8B, the piston 240 includes a pistonhead 242 to which is connected an upwardly extending connecting rod 246which extends through central opening 228.

The upwardly extending connecting rod 246 includes an open sidedrectangular cage 248 at its upper end. The bottom wall 250 of the cage248 includes an opening 256 which connects to an elongated conduit 260which extends downwardly through the connecting rod 246.

The lower end of the connecting rod 246 terminates inside the pistonhead 242. The lower end of the connecting rod 246 includes a laterallydirected opening 262 which is in liquid connection with theaforementioned elongated conduit 260.

A guide roller 264 which may a generally hollow cylindrical member iscontained within the cage 248 so that it can reciprocate from one end ofthe cage 248 to the other as seen in FIG. 8B.

As seen in FIG. 7, the rectangular cage 248 and guide roller 264 arereceived in and are retained in the cut-out 64 by an elongated pin 268which extends through an opening in the hub 26 of the nozzle assemblyand extends into a blind hole (not shown) in the rear portion 60 ofhollow section 54. The elongated pin 268 is spaced radially from theaxis of rotation of the nozzle and crankshaft 24.

The length of roller 264 is slightly less than the length of cut-out 64(FIGS. 2 and 3). Thus, the guide roller 264 is constrained in thecut-out 64 so that it can only move back and forth in the rectangularcage 248.

As seen in FIGS. 7 and 8A, the piston head 242 includes an upper end cap270, a mid-portion 272 and a lower end cap 274.

The upper end cap 270 comprises a relatively flat disc, having adownwardly facing peripheral notch in which is received an O-ring seal282.

The upper end cap 270 includes a first opening 286 which lies along oneof its diameters but spaced from its center. From the first opening 286there is connected a downwardly extending conduit 288 having a beveledend 290 with its inner juncture with the conduit 288 being closer to theupper end cap 270 than its outer edge 296.

On generally the same diameter, but on the other side of the center ofthe upper end cap 270 is another opening 300. A pin 302 having a head306 whose diameter is greater than the opening 300 and which includes anupwardly extending shaft 308 having a diameter less that the opening 300is provided. The pin 302 is positioned in the opening with the head 304against the underside of the upper end cap 270 and its shaft 308extending through the opening 300 so that its distal end 310 is exposed.Thus, when a downward force is applied to the distal end 310 the pin 302will move downwardly through opening 300.

An opening 314 is provided near the periphery of the upper end cap 270through which the lower end of the connecting rod 246 is received.

Openings 318 are provided in the upper end cap 270 to receive suitablescrews for connecting the upper end cap to mid-portion 272.

The lower end cap 274 is a mirror image of the upper end cap 270. Thus,it need not be described further other than to say that its parts areidentified by the same numerals as those associated with the upper endcap 270 except that they are followed by a “′”.

Thus, end caps 270 and 270′ and seals 282 and 282′ provide a sealingrelation between the piston head 242 and the walls of the piston chamber20.

However, it should be noted that pins 308 and 308′ are opposite eachother, and conduits 288 and 288′ and their respective beveled ends 290and 290′ are opposite each other.

The mid-portion 272 of the piston head 242 includes a diametricallyextending elongated relatively wide opening 330. A flat blade 334,preferably made of a thin rust resistant metal 334 is slightly longerthan the opening 330 has its ends wedged into notches at the ends ofopening 330 so that it is slightly bowed.

In FIG. 10A the blade 334 is shown bowed upwardly to create a “frown.”However, upon the application of force, it can be pushed until it snapsinto a downwardly bowed position where it achieves a “smile” as seen inFIG. 10B.

The mid-portion 272 includes an opening 336 which can be aligned withopenings 314 in the upper end cap 270 and opening 214′ in the lower endcap 274 when the piston head 240 is assembled such as when screwspassing through 318 and 318′ are connected to internally threadedopenings 328 in the mid-portion 272.

As best seen in FIGS. 8A and 9, the connecting rod 246 is received inopenings 314, 336 and 314′ in the piston head 242 so that laterallyextending opening 262 in the lower end of the connecting rod 246 isaligned with conduit 342 in the mid-portion 272 to permit liquid flowingthrough laterally extending opening 262 to enter the opening 330 in themid-portion 272. The connecting rod 246 is retained in position by asuitable set screw (not shown) which is threadingly received in opening356.

The opening 336 is also connected by another conduit 344 to a recess 348formed in the circumferential wall 350 of the mid-portion 272. A gasket354 (shown in section) extends around the circumferential wall 350 ofthe mid-portion 272 to provide further sealing between the piston head240 and the piston chamber 20.

In operation the washer 10 is connected to liquid supply pipe 204 bybeing threadingly connected to collar 194. Collar 194 is connected toelongated hollow sleeve 180 and its bevel gear 190 so that the collar194, hollow sleeve 180 and bevel gear 190 are constrained againstmovement by the liquid supply pipe 204.

A suitable liquid such as a cleaning solution or the like enters thewasher 10 through the supply pipe 204 and liquid inlet 16 filling thehousing 14. In the washer 10 the liquid is divided into two liquidpaths. One path includes the axial opening 26 in the nozzle andcrankshaft assembly 24 which directs the liquid to the hub 26 of thenozzle assembly and then out the nozzles 30 to be sprayed onto thesurface to be cleaned.

The second liquid path directs about one percent of the liquid enteringthe washer 10 into the piston chamber 20. The second liquid pathincludes the opening 256 at the bottom of rectangular cage 248,elongated conduit 260 in connecting rod 246, laterally extending opening262 at the bottom of connecting rod 246 and conduit 342 in themid-portion 272 of the piston head 240 and into opening 330.

Liquid initially received in opening 330 is directed to either one sideor the other of the piston head 242, depending on the position of theblade 334, to drive the piston in the opposite direction in a mannerwhich will now be described.

As best seen in FIGS. 10A and 10B, the liquid will encounter the blade334 bowed either up (“frown”) or down (“smile”). If it is bowed down(FIG. 10B), then it closes conduit 288′ because it bears against thebeveled end 290′ at the upper end of the conduit 288′. The bevel of theend 290′ is at the same angle the curvature of the blade 334 makes attheir point of contact.

Consequently, liquid entering the mid-portion 272 of the piston head 242through the elongated conduit 260 in the connecting rod 246 and conduit342 will enter conduit 288 at its beveled end 290 and flow throughconduit 288 into the space between the piston head 242 and the top wall214 of the piston chamber 20. This causes the piston 240 to movedownward. If there is liquid in the space between the piston head 240and bottom wall 212 of the piston chamber 20 it simply leaks out throughdrain opening 236 in the bottom wall 212.

As seen in FIG. 10A, when the piston head 240 nears the bottom wall 212of the piston chamber 20, the distal end 310′ of the shaft 308′ of pin302′ strikes the bottom wall 212 of the piston chamber 20. This pressesthe pin head 306′ into engagement with the blade 334. It pushes andbends the blade 334, as will be described, so that it moves to theposition shown in FIG. 10B.

Since the pin 302′ is located to the side of the blade 334, it initiallyforces the part 338 of the blade 334 against which is presses to move sothat the blade 334, which is slightly longer than opening assumes theconfiguration of an “S” as seen in FIG. 11A. The force which the pin302′ applies to the blade 334 is stored in the “S” configuration asenergy.

Because the blade 334 is resilient, some of the stored energy isreleased by forcing the rest 340 of the blade 334 into closer relationto the beveled end 290′ thereby further assuring that there is no liquidflow through it.

Continued movement of the pin 302′ will force the blade 334 over itscenter of resistance. This releases the remainder of the energy storedin the blade 334 so that the blade 334 now moves independently of thepin and snaps away from beveled end 290′ to the position shown in FIG.10B where it now closes beveled end 290 on conduit 288. Pin 302 which isfreely moveable in opening 300 offers no resistance to the blade 334 asit moves to the position shown in FIG. 10B.

With the blade 334 in the position shown in FIG. 10B, the beveled end290 of downwardly extending conduit 288 is closed and the opening 290′in upwardly extending conduit 288′ is open. Thus, liquid enteringmid-portion 272 of piston head 242 through conduit 342 flows throughconduit 288′ into the space between the bottom wall 212 and the pistonhead 242. This drives the piston head 242 upwardly toward top wall 214.Liquid trapped in the space between the top wall 214 and the piston head242 is permitted to leak from the piston chamber 20 through drainopening 234.

When the piston head 242 nears the top wall 214 of the piston chamber20, the distal end 310 of the shaft 308 of upwardly extending pin 302will strike the top wall 214. This causes pin 302 to engage the blade334 at 340 and apply force to it as seen in FIG. 11B until it snaps tothe position shown in FIG. 10B. This closes conduit 288′ and opensconduit 288 to cause the piston head 242 to move toward bottom wall 212.

Thus, the relationship of the pins 302, 302′, conduits 288, 288′, andblade 334 and drain openings 234 and 236 form a mechanism which enablesthe piston 240 to reciprocate within the piston chamber 20.

Since the connecting rod shaft 246, rectangular cage 248 and guideroller 264 are all connected to the piston 240, they reciprocate also.

As explained earlier, the rectangular cage 248 and guide roller 264 areconnected to the nozzle and crankshaft assembly 24 by elongated pin 268(FIG. 7). The elongated pin 268 is spaced radially from the axis ofrotation of the nozzle and crankshaft 24. Thus, as the piston 240reciprocates in the piston chamber 20, it causes the nozzle andcrankshaft assembly to move about its axis of rotation in a well knownmanner. The range of movement of the nozzle and crankshaft assembly islimited so that it can only pivot through an arc of slightly greaterthan 90° when the hub 26 of the nozzle assembly 28 supports two nozzles30 as shown in FIGS. 1 and 2. If the hub of the nozzle assembly supportsthree nozzles, the range of arcuate movement can be reduced to aboutslightly greater than 60°. The guide roller 264 moves move back andforth in the rectangular cage 248 as the nozzle and crankshaft assemblyrotates to maintain its driving connection with them.

The range of movement of the nozzle and crankshaft assembly 24 islimited by the range of movement of the piston head 240 and the lengthof the connecting rod 246.

As is apparent, the range of movement of the piston head 240 is limitedby the distance between the upper and lower walls 212 and 214 of thepiston chamber 20 and/or the length of the pins 302 and 302′. Thus, ifthe pins are longer, the reversal of movement of the piston head 240occurs sooner.

The arc of reciprocation is further controlled by limiting the length ofthe connecting rod 246 to a distance that is less than the distancebetween the upper limit of piston 240 movement and the upper part ofcut-out 64.

Thus, at the preferred arc of reciprocation, thorough cleaning occurswithout the connecting rod 246 striking the cut-out 50 thereby avoidingmetal-to-metal contact.

Further, the speed at which the reciprocation of the piston occurs canbe controlled by changing the size of the drain openings 234 and 236.Thus larger opening permit the liquid to leave the piston chamber 20faster to increase the speed of the piston.

When two nozzles 30 are used, they reciprocate through an arc ofslightly more than 90°. When three nozzles are used, they reciprocatethrough an arc of slightly more than 60°. However, these arcs are notcritical and the cleaner will work equally as well to clean tanks if thearcs were somewhat smaller or somewhat larger.

Thus, as is apparent and by way of summary, piston 240, connecting rodshaft 246, open sided rectangular cage 248, guide roller 264, pin 268(FIG. 7), nozzle and crank shaft assembly 24 comprise a means forconnecting the piston 240 to nozzles 30 so that when the piston 240reciprocates, the nozzles also reciprocate.

The washer 10 is driven about the liquid supply pipe 204 by thereciprocation of the nozzle and crankshaft assembly 24. As seen in FIG.6, the elongated hollow sleeve 180 and bevel gear 190 are fixed to theliquid supply pipe 204 and thus can not rotate. Since the bevel gear 130in engagement with bevel gear 190, it also can not rotate.

As explained earlier, the nozzle and crankshaft assembly 24 supportsbevel gear 130. The nozzle and crankshaft assembly 24 is limited formovement in one direction relative to the bevel gear 130 by the ratchetassembly 80.

Thus, as seen in FIGS. 5 and 6, when the nozzle and crankshaft assembly24 rotates in the direction A (FIG. 4) under the force of the piston 240reciprocating in piston chamber 20, the pawl 124 yields to permit therotation.

However, when the nozzle and crankshaft assembly 24 moves in thedirection of arrow B (FIG. 4) under the force of the piston 240reciprocating in piston chamber 20, the pawl 124 prevents relativerotation between the nozzle and crankshaft assembly 24 and the bevelgear 130.

Therefore, the bevel gear 130 is required to rotate around bevel gear190 and the supply pips 204 in a series of “steps.” The number of stepsnecessary to rotate the housing 14 and nozzles 30 around the supply pipe204 to wash the interior of a tank can be varied in accordance with thenumber of teeth on each of the bevel gears 130 and 190 and the number ofteeth 134 in the interior circumference of the bevel gear 130.

Thus, by way of summary, the piston 240 reciprocates inside pistonchamber 20 under the force of the liquid entering the washer 10. Thereciprocation of the piston causes the nozzle and crankshaft assembly 24to reciprocate through about 90° as liquid is sprayed the nozzle 30.

The reciprocation of the nozzle and crankshaft assembly 24 causes thebevel gear 130 to move around the bevel gear 190 to cause the housing 14to rotate around the liquid supply conduit 204 in a plurality of stepsto wash the interior of the tank that is being cleaned.

While the invention has been described with regard to one presentlypreferred form, it is apparent that other forms of embodiments will beobvious skilled in the art in view of the foregoing description.

Accordingly, the scope of the invention should not be limited by theforegoing description, but rather, only by the scope of the appendedclaims.

1. A tank washer comprising a housing, first and second axes, aplurality of nozzles, said nozzles being supported on said housing forreciprocation around one of said axes, a piston in said housing, saidpiston being reciprocal along said other axis, and means for connectingsaid piston to said nozzles so that reciprocation of said piston causessaid nozzles to reciprocate.
 2. A tank washer as defined in claim 1including a first chamber in said housing, said piston being disposed infirst chamber for reciprocal movement, a second chamber, and saidnozzles being in liquid connection with said second chamber so that saidsecond chamber and said nozzles define a liquid conduit.
 3. A tankwasher as defined in claim 2 wherein said nozzles are supported by anelongated hollow element that is supported for reciprocation in saidhousing, said elongated hollow element including a central opening thatis in liquid connection with said nozzles, and said hollow memberincludes means for enabling it to be connected to said piston so thatmovement of said piston causes said elongated member and said nozzles toreciprocate.
 4. A tank washer as defined in claim 2 including a liquidinlet conduit connected to said housing for supplying liquid to saidhousing, means for enabling said housing to rotate relative to said tosaid liquid inlet conduit, and mutually engagable means supported bysaid liquid inlet conduit and said hollow member for causing saidhousing to rotate relative to said liquid inlet conduit as said pistonreciprocates.
 5. A tank washer as defined in claim 4 wherein saidmutually engagable means comprising a first gear supported on saidhollow member, means connected between said first gear and said hollowmember for permitting said gear to rotate relative to said hollow memberin one direction, and to be driven by said hollow member in a seconddirection.
 6. A tank washer as defined in claim 5 wherein said mutuallyengagable means further comprising a second gear, said second gear beingfixed to said liquid inlet conduit so that when said first gear drivessaid second gear, said housing rotates around said liquid inlet conduit.7. A tank washer as defined in claim 5 wherein said means connectedbetween said first gear and said hollow member for permitting said gearto rotate relative to said hollow member in one direction, and to bedriven by said hollow member in a second direction comprises a pawlrecess on the interior wall of said hollow member, an opening in saidwall of said hollow member generally opposite to pawl recess, a pawl,one part of said pawl being received in said pawl recess and anotherpart of said pawl extending through said opening in said wall, and meansconnected between hollow member and said pawl for urging said other partof said pawl into engagement with said first gear.
 8. A tank washer asdefined in claim 7 wherein said means connected between hollow memberand said pawl for urging said other part of said pawl into engagementwith said first gear comprises an elongated torsion member, one end ofsaid elongated torsion member being connected to said hollow member, andthe other end of said elongated torsion member being connected to saidpawl.
 9. A tank washer as defined in claim 1 wherein said housingincludes a piston chamber, said piston including a piston head and aconnecting rod having one end connected to said piston head, said pistonbeing mounted in said piston chamber for reciprocation, and means forproviding a sealing relation between said piston head and the walls ofsaid piston chamber.
 10. A tank washer as defined in claim 9 whereinsaid piston head includes a liquid inlet and two liquid outlets, andmeans for directing liquid entering said piston head through said pistonhead alternately through said liquid outlets to cause said piston toreciprocate in said piston chamber.
 11. A tank washer as defined inclaim 10 wherein each of said liquid outlets is on a different side ofsaid piston head.
 12. A tank washer as defined in claim 10 wherein saidmeans for directing liquid comprises a means for closing said liquidoutlets in said piston head, said means for closing said liquid outletsis operative to selectively close said liquid outlets so that when oneof said liquid outlets is closed the other liquid outlet is open.
 13. Atank washer as defined in claim 10 wherein said piston head includes amid-portion and upper and lower end caps, said mid-portion including acentral opening, said central opening being in liquid communication withboth of said liquid outlets, each of said liquid outlets being in one ofsaid piston end caps, and means in said central opening for selectivelyclosing said liquid outlets so that when one of said liquid outlets isclosed the other liquid outlet is open.
 14. A tank washer as defined inclaim 13 wherein said means for selectively closing said liquid outletscomprises a resilient flexible member supported in said central openingin said mid-portion, said resilient flexible member being movablebetween a first position where one of said liquid outlets is closed anda second position where the other liquid outlet is closed.
 15. A tankwasher as defined in claim 14 including means for moving said resilientflexible member toward one of said positions from the other position,said last named means being operative to store energy in said resilientflexible member as said last named means moves toward said otherposition, said means for moving said resilient flexible membercomprising pins extending through said end caps and being mutuallyengagable with the end walls of said piston chamber and said resilientflexible member so that as said piston reciprocates in said pistonchamber said pins alternately engage the end walls of said pistonchamber and said resilient flexible member to increase the energy storedin said resilient flexible member as a portion of said resilientflexible member moves toward said other position while the rest of saidresilient flexible member maintains said one of said liquid outletclosed, and the release of said stored energy moves said resilientflexible member away from said means for moving said resilient flexiblemember to said other position where said one of said liquid outlets isopen and the other of said liquid outlets is closed.